1. Field of the Invention
The present invention relates to an exposure apparatus and a method of manufacturing a device.
2. Description of the Related Art
For an exposure apparatus used in a semiconductor manufacturing process, three performances are considered of prime importance: the resolution as an index of micropatterning, the overlay accuracy indicating the alignment performance of each layer, and the throughput indicating the productivity. To improve the throughput, for example, the exposure energy per unit time is increased, the time taken for a substrate stage to move step by step across shots is shortened, the time taken to exchange and convey substrates is shortened, or the scanning time of a scanner is shortened.
To shorten the conveyance time upon substrate exchange with the goal of improving the throughput, an effective measure is to shorten the conveyance distance. Nevertheless, to attain high resolution and high overlay accuracy, the layout in an exposure apparatus must inevitably be determined so as to optimize the location of a projection optical system, an illumination system serving as a light source, a substrate stage, and a substrate position measurement unit. For this reason, it is extremely difficult to shorten the conveyance time by shortening the conveyance distance.
To shorten the conveyance time, upgrading of a driving motor of a conveyance arm has been proposed. However, the bulk of a driving motor increases upon upgrading the motor. This poses problems such as the motor not being locatable in a limited apparatus space, the amount of heat generation increasing with increased driving energy, and the increased risk of substrate fall as the conveyance velocity and acceleration rise.
To shorten the conveyance time, Japanese Patent Laid-Open No. 2006-66636 discloses a mechanism of almost simultaneously performing supply of an unexposed substrate to a substrate stage and recovery of an exposed substrate from the substrate stage using a loading arm and an unloading arm.